#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    long long ans=0;
    int sum=0;
    while(1)
    {
        sum=sum+p;
        if(sum>s)
            break;
        ans++;
        p=p-d;
        if(p<m)
            p=m;
    }
    cout<<ans<<endl;
    return 0;
}